Ohm's Law & Power: Bicycle LED Headlight & 4 AA Batteries

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A bicycle LED headlight requires 5 V and 250 mA, leading to a calculated resistance using Ohm's law (R = V/I). The power consumption can be determined with P = VI, where the time is not specified but can be inferred from battery specifications. Each AA rechargeable battery provides 1.25 V and 2300 mA-Hour, indicating that with four batteries in series, the total voltage is 5 V. The batteries would last approximately 10 hours when supplying 250 mA, calculated by dividing the total capacity by the current. Understanding these calculations helps in determining the operational efficiency of the LED headlight.
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A bicycle LED headlight requires 5 V, 250 mA to operate. Using Ohm’s law, determine the
equivalent resistance of the light. What is the power consumption rate in W? How many
electrons pass through per second? It is powered by four AA rechargeable battery in series. Each battery provides 1.25 V and has a specification of 2300 mA-Hour. How many second would the battery last?

The first part i used R = v/I

The second part I know P = VI but am not sure what to use for time because it does't give one.

The third part i don't know about. I am not looking for the answer but help on how to get there thank you
 
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can somebody give me an idea
 
Isn't 1 watt = one joule per second?

Maybe better: 1 ampere = 6.242*1018 electrons/second
 
Last edited:
Each battery provides 1.25 V and has a specification of 2300 mA-Hour. How many second would the battery last?

This means each battery would last for an hour if it was supplying 2300 mA. It would last for 10 hours if it was supplying 230 mA.

So product of (current * time) = 2300 mAH
or
time = 2300 mAH / current

So, how long would it last if it was supplying 250 mA?
 

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